LONDON  An infectious fungus aggravated by global warming has killed entire populations of frogs in Central and South America and driven some species to extinction, scientists said on Wednesday.

In research that showed the effects of rising temperatures on delicate ecosystems, a team of researchers found that a warming atmosphere encouraged the spread of a fungus that has wiped out species of harlequin frogs and golden toads.

"This is the first clear evidence that widespread extinction is taking place because of global warming," Dr Alan Pounds, an ecologist of the Monteverde Cloud Forest Preserve in Costa Rica, said in an interview.

"Climate change is already altering the dynamics of infectious disease and causing species to disappear."

Pounds and his team established the link between global warming and the disappearance of frogs in the cloud forests of Costa Rica by analysing sea surface and air temperatures, which rose by 0.18 degrees per decade between 1975 and 2000.

ADVERTISEMENT

Warmer temperatures increased cloud cover over the tropical mountain which the scientists believe promoted conditions to spur the growth of the chytrid fungus that kills frogs.

They are confident that global warming is a key factor in the disappearance of many amphibian populations in tropical forests.

"There is absolutely a linkage between global warming and this disease -- they go hand-in-hand," said Dr Arturo Sanchez-Azofeifa, of Canada's University of Alberta and a co-author of the research published in the journal Nature.

"With this increase in temperature, the bacteria has been able to increase its niche and wipe out large populations of amphibians in the Americas," he added in a statement.

About a third of the 5,743 known species of frogs, toads and other amphibians are classified as threatened, according to the Global Amphibian Assessment.

Up to 167 species may already be extinct and another 113 species have not been found in recent years. Habitat loss is the greatest threat to amphibians but fungal disease is also a serious problem.

Andrew Blaustein, of Oregon State University, and Andy Dobson, of Princeton University in New Jersey, described the research as a breakthrough.

"The powerful synergy between pathogen transmission and climate change should give us cause for concern about human health in a warmer world," they said in a commentary in Nature.

"The frogs are sending an alarm call to all concerned about the future of biodiversity and the need to protect the greatest of all open-access resources -- the atmosphere," they added.